POTD

These puzzles may seem like a waste of time, but they serve a practical function in the US government.

7652_pres.jpg
 
wrcmad said:
http://beust.com/pics/probability-quiz.jpg
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I agree with Greg - 0%.

25% would work if D (or A) was something different. As it is, though, a random choice will give 25% 50% of the time, while 50% will be chosen 25% of the time, so that doesn't work and is essentially paradoxical.

Since 0% is not one of the given options, there is a 0% probability of randomly selecting it from the given options, so it works as an answer.

Alternatively, we can just say that there is no satisfactory solution due to the paradox, which I guess would be the only solution if the question specified that the answer must be selected from the list. Since it doesn't specify this, I think that 0% is the better answer.
 
Argentum said:
Well done wrcmad
Last one for tonight:

You're a bank manager in a SHTF crisis and your bank has 1000 safety deposit boxes filled with gold. Since fiat is now irrelevant you dont worry about all the stacks of dollars euros and pounds that are stacked in the vault. You do know that one of the deposit boxes has gold/silver bullion in it and rest are tungsten bars at the core but that deposit box with real gold is fitted with a dispenser of some kind of biological/chemical agent that will kill you over a period between 12-24 hrs without any symptoms in the mean time. The dispenser is so small that noone really notices it when searching for it.

You dont have access to any protection equipment or any technolgy that distinguishes gold from tungsten however you do have access to a large group of employees that work for you. These can be used to check the contents of the boxes. Now bear in mind that time is of the essence and that you want least amount of people to die for your cause.

The only way to know which box contains real gold is the one where the person dies from opening it. Whats the minimum number of employees you will need to die for you to find the real gold.

So explain how many employees you will need and how many will die and your strategy
Click to expand...

If you can open a box multiple times and still kill the person. you can do it in 36 - 72 hours
10 people open 100 boxes each. (Keep Records)
10 people search 10 each of the 100 of the guy that dies
10 people search 1 each of the boxes of the guy that dies

3 people die in total
 
Apologies for forgetting to put the answer for the 1000 box puzzle so here its is:

you can do it in 12-24 hrs. you make a cube of all the boxes 10 x 10 x 10. You need 30 people. Each employee will open a 100 but not any 100. This is now like coordinates in 3 directions x y and z. (x=left/right, y up/down and z forward backward.

So person 1 opens all the boxes that have an x=1 so in other words the first column 2nd person second column etc.

people 11-20 open y=1 to y=10

and 21-30 will open z=1 to z=10


Now lets say from x direction person 5 died and y direction no. 2 died and z direction no.9 died. You then have an exact coordinate which box has the real gold. So need 30 people but 3 die.
 
wrcmad said:
I find the following puzzle fantastic, and tends to highlight deeply rooted "intuitive assumptions/beliefs" that are instinctive in humans, and that often trip us up - especially in things like trading or investing:

Suppose you're on a game show, and you're given the choice of three boxes:
Inside one box is a 10oz gold bar;
Inside the others, a 1oz silver coin.
You pick a box, say No. 1, and the host, who knows what's inside each box, opens another box, say No. 3, which contains a 1oz silver coin.
He then says to you, "Do you want to pick box No. 2?"
Is it to your advantage to switch your choice?
Click to expand...

Took a while, but I finally understood how/why it was better to switch :D

Let's assume the gold bar is in box no. 1 (and only the presenter knows this of course)
Also assume that you have an equal chance of picking each box, since you don't know what's inside

Scenario A:
Pick box 1 (1/3 chance)
Presenter opens box 2 or box 3
Either way, you'll be worse off switching

Scenario B:
Pick box 2 (1/3 chance)
Presenter is 'forced' to open box 3
Therefore you'd be better switching boxes

Scenario C:
Pick box 3 (1/3 chance)
Presenter is 'forced' to open box 2
Again you'd be better switching boxes

Overall you have a 2/3 chance of getting that gold bar by switching boxes (which is shown in the graphs in post #38)
 
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